Proposed is the first application of an innovative and powerful protein engineering technique to create clinically relevant epidermal growth factor (EGF) antagonist variants that will inhibit signaling from the epidermal growth factor receptor (EGFr). The developed combinatorial biosynthesis technique is the first DNA shuffling method applicable to such small, diverse genes, and has generated demonstrably better DNA shuffled EGF libraries than has been done for any other DNA shuffling technique for any gene, regardless of size. We propose to screen this diverse combinatorial library to generate high affinity proteins that inhibit signaling from the ErbBl receptor. Enabling an approach to create antagonistic growth factors will complement receptor blocking strategies involving antibodies or small molecules. Our collaboration partner at the University of Texas M.D. Anderson Cancer Center, Dr. Mien-Chie Hung, has the expertise to thoroughly evaluate each of our candidates in xenograft tumor animal studies. Successful outcome on this project will provide the impetus to pursue a host of broadly applicable small protein ligands against similar receptor-dependant malignancies. PROPOSED COMMERCIAL APPLICATION: We aim to engineer EGF variants for use as cancer therapeutics. Upon Phase I success, Phae II would result in an Investigative New Drug. Benefits to the treatment of cancer and thus the commercial applications of this therapy are clear. However, we are also attempting to use novel protein engineering tools to more generally enable a relatively neglected class of human therapeutics. The potential for improvements in human health and the range of commercial applications would be enormous.